1. Sauté shallot in butter in a large Dutch oven over medium heat, stirring constantly, 2 minutes or until tender. Whisk in flour and salt until smooth. Cook 1 minute, whisking constantly. Gradually whisk in chicken broth. Add potatoes and bay leaf. Cover and bring to a boil; reduce heat, and simmer, uncovered, 15 minutes or until potatoes are almost tender. Add salmon; simmer 5 minutes or until fish flakes with a fork and potatoes are tender.
2. Discard bay leaf. Stir in cream, 2 tablespoons chives, vinegar, and next 3 ingredients. Cook over medium heat, stirring often, 2 minutes or until thoroughly heated. (Do not boil.) Ladle into bowls; sprinkle with remaining 2 tablespoons chives.